This invention relates to electrical outlet receptacle covers, and more particularly to a fail-safe safety cover plate for attachment to an electrical wall receptacle for protecting against accidental insertion of a plug or foreign objects into the sockets of the receptacle, and includes means for ensuring proper electrical contact of the prongs of a plug when correctly inserted.
Many household accidents have resulted from electrical shocks occurring when meddling or curious children have inserted small metallic items into the electrical outlet receptacle sockets. The prior art has recognized this problem and has dealt with it in various ways. Small plastic socket-like members are marketed for insertion into unused outlet sockets to close the sockets from insertion of such items. However, these members are readily removed by a child and have limited affect. Thus, various other proposals have been made using moveable shutter type members in an attempt to solve this problem, the shutter members acting to close the sockets until moved by the prongs of a plug to align prong receiving slots of the shutter with the socket slots. For example, U.S. Pat. Nos. 2,820,842; 3,068,442; and 3,865,456 disclose receptacle cover plates having linearly slideable shutters, while U.S. Pat. Nos. 1,159,207; 1,989,693; 2,498,642; 2,524,250; 2,641,627; 2,752,581; and 3,113,174 disclose either cover plates or receptacles having rotatable shutters, and U.S. Pat. No. 2,455,582 discloses a plate which appears to have a rotary and linearly removable shutter.
One of the difficulties of the known cover plates having such shutters is the use of metallic springs for biasing the shutters to the socket closing position. If, for example, such a spring fails a potentially dangerous condition could result if a portion of the spring is impelled and lodged into the receptacle. In order to overcome this difficulty the prior art placed a back plate between the springs and the receptacle. Such a construction is illustrated, for example, in Bierce U.S. Pat. No. 2,524,250 and Lewis U.S. Pat. No. 2,641,627. However, when a back plate is used there is the possibility of an inadequate contact being made between the prongs of a plug and the socket of the receptacle. Cover plates having a likelihood of this occurring will not obtain certification by certifying testing organizations. Thus, ideally, the shutters should abut the receptacle socket faces and provide minimum spacing between the face of an inserted plug and the face of the receptacle socket.